Where a binary or pancreatic duct becomes occluded, it is often desirable to facilitate drainage through the duct by the placement of a stent within the occluded area. Conventional stents for this purpose are commonly made of polyethelene and teflon and include flaps or barbs at each end of the stent which serve to prevent migration and retain the stent in place. Stents have also been commonly pre-formed at their ends into various retaining configurations, such as pigtails or spirals, to help maintain the stent in position. Stents have also been formed into various expandable configurations so that, when the stent has reached the occluded area, the stent is expanded to press outwardly against the ductal wall and to thereby maintain its position within the duct. Biliary and pancreatic stents are typically pushed into place by a "pusher" catheter which is advanced from behind the stent and pushes against the proximal end of the stent until the stent has reached its desired location.
During the placement procedure, conventional retaining elements have been known to have an abrasive effect on the surrounding ductal tissue as they pass through the duct, thus causing or aggravating inflamation of the duct. Conventional retaining elements have also been known to cause aggravation to the ductal tissue while the stent is left in place, and particularly, when the stent is removed.
There is a need for an improved stent which can be atraumatically placed within an occluded biliary or pancreatic duct and maintained in place without causing aggravation to the ductal tissue, and which further can be removed without damaging the duct. There is also a further need for improved instrumentation for facilitating the atraumatic placement of a stent within a biliary/pancreatic duct.